feat: add programmatic usage example to README

Added an example in README for generating a weekly calendar
programmatically using Kalente. This assists developers by
demonstrating how to integrate Kalente into their projects.

fix: default options parameter in convert_html_to_pdf

Updated the `options` parameter in `convert_html_to_pdf` to
default to an empty dictionary. This prevents potential NoneType
errors and ensures consistent behavior.

chore: bump version to 0.2.1

Updated version in pyproject.toml to reflect the new features
and bug fixes.

README.md

@@ -72,6 +72,29 @@ kalente --help
 For example, you may want to look into the `--end-date` and `--count` options
 to generate calendars for multiple weeks or months.
 
+## Programmatic Usage
+
+Kalente can also be used programmatically. Here's an example of how you can
+generate a weekly calendar using Kalente:
+
+```python
+from kalente import Calendar
+from datetime import date
+
+# Create a Calendar object, optionally specifying the country to use
+# for holidays, and a date format.
+calendar = Calendar(country_code="AT", date_format="%d %B %Y")
+
+# Get week data for the week of January 1st, 2021.
+data = calendar.get_week(date(2021, 1, 1))
+
+# Generate HTML for the week.
+html = Calendar.generate_html(data, type="weekly")
+
+# Generate a PDF file for the week.
+Calendar.convert_html_to_pdf(html, "weekly.pdf")
+```
+
 ## License
 
 Kalente is licensed under the MIT license. See the [LICENSE](LICENSE) file for

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "kalente"
-version = "0.2.0"
+version = "0.2.1"
 authors = [
   { name="Kumi Mitterer", email="kalente@kumi.email" },
 ]

src/kalente/classes/calendar.py

@@ -124,7 +124,7 @@ class Calendar:
             raise ValueError("Invalid content type: {}".format(content_type))
 
     @staticmethod
-    def convert_html_to_pdf(content, output_filename, options=None):
+    def convert_html_to_pdf(content, output_filename, options={}):
         options.setdefault("page-size", "A4")
         options.setdefault("orientation", "Landscape")
         pdfkit.from_string(content, output_filename, options=options)